Silicon carbide semiconductor device and method for manufacturing the same

Abstract

A semiconductor device according to the present invention includes a silicon carbide semiconductor substrate having a silicon carbide semiconductor layer; a p-type impurity region provided in the silicon carbide semiconductor layer and including a p-type impurity; a p-type ohmic electrode electrically connected to the p-type impurity region; an n-type impurity region provided in the silicon carbide semiconductor layer adjacent to the p-type impurity region, and including an n-type impurity; and an n-type ohmic electrode electrically connected to the n-type impurity region. The p-type ohmic electrode contains an alloy of nickel, aluminum, silicon and carbon, and the n-type ohmic electrode contains an alloy of titanium, silicon and carbon.

Description

TECHNICAL FIELD[0001]The present invention relates to a silicon carbide semiconductor device, and in particular to a silicon carbide semiconductor device having n-type and p-type ohmic electrodes and a method for producing the same.BACKGROUND ART[0002]Conventionally, power devices using silicon (Si) semiconductors have been used as devices for power electronics. Devices for power electronics are required to operate at a higher frequency with a larger current. Various studies for research and development have been made to improve the performance of silicon power devices.[0003]However, the performance of the silicon power devices is now approaching the theoretical limit thereof. In addition, power devices are occasionally required to operate in severe environments, for example, at a high temperature or under radiation. Silicon semiconductors are not suitable to use in such severe environments. For these reasons, studies are being made regarding devices using semiconductor materials ot...

AI Technical Summary

Benefits of technology

[0045]According to the present invention, in a semiconductor device including an n-type impurity region and a p-type impurity region provided adjacent to each other in a silicon carbide semiconductor layer, an n-type ohmic electrode containing titanium, silicon and carbon and a p-type ohmic electrode containing nickel, aluminum, silicon and carbon are respectively provided in the n-type impurity region and the p-type impurity region. The n-type ohmic electrode and the p-type ohmic electrode can realize a low resistance ohmic contact respectively to an n-type silicon carbide semiconductor and a p-type silicon carbide semiconductor. Therefore, a low resistance ohmic contact can be realized without making high the impurity concentration of the n-type impurity region or the p-type impurity region. Accordingly, in a switching device such as a MISFET, a MOSFET or the like, a low resistance p-type ohmic electrode can be formed without increasing the n-type contact resistance which significantly influences the ON resistance, and thus the switching characteristic can be improved.

Problems solved by technology

However, the performance of the silicon power devices is now approaching the theoretical limit thereof.

In addition, power devices are occasionally required to operate in severe environments, for example, at a high temperature or under radiation.

Silicon semiconductors are not suitable to use in such severe environments.

However, the characteristics of the ohmic contact to especially the p-type silicon carbide semiconductor material have not been satisfactory.

Specifically, when the material for a p-type ohmic electrode is thermally treated at a high temperature of about 1000° C. during the formation of the ohmic electrode, the material for the ohmic electrode is aggregated, which decreases the uniformity or generates a stress due to the aggregation.

As a result, crystal distortion or transition occurs in the silicon carbide semiconductor, which causes a problem that the crystallinity is decreased.

This natural oxide layer has a problem of exerting an adverse effect on the ohmic characteristics when the ohmic electrode and the silicon carbide semiconductor are alloyed with each other.

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